Door lock



May 19,, 1970 M. H. DITTMORE 3,513,357

DOOR LOCK Filed Sept. 15, 1967 3 Sheets-Sheet 1 30 I \QQ/DXN f E INVENTOR.

MAYLIN H. DETTMCRE BY ATTORNEY United States Patent 3,513,357 DGQR LOCK Maylin H. Dittmore, 697 Meadowlark St., Livermore, Calif. 94550 Filed Sept. 13, 1967, Ser. No. 667,483 Int. Cl. E05]: 47/02, 49/02 US. Cl. 317134 8 Claims ABSTRACT OF THE DISCLOSURE A door lock comprising an electronic circuit that makes it possible to release a door latching bolt by entering a pre-set sequence into a series of pushbutton switches from outside the door. The latching bolt is also releasable by actuating a single pushbutton switch from inside the door. The bolt can be set by a single pushbutton switch from either outside or inside the door. The circuit includes an electronic counting mechanism that is activated by the pushbutton switches and provides sequential signals to a logic network that deciphers them and generates a signal to the latch releasing mechanism if, and only if, the proper code has been entered on the pushbutton switches.

Brief description This invention relates to door locks and is particularly related to locks that are operated in accordance with the proper sequential actuation of a series of pushbuttons. Such pushbutton type, combination door locks are shown, for example, in US. Pats. 3,242,388 and 2,855,588, but since these utilize relays and other mechanical components having sound-creating moving parts, it is possible for the movement of the parts to be detected, and it may be possible for a person detecting such movements to determine the correct operating sequence.

It is an object of the present invention to provide a pushbutton type, combination lock that has no soundcreating moving parts that can be detected by a person attempting to determine the correct sequence of actuation of the pushbuttons necessary to unlatch the door in which the lock is placed.

Another object is to provide such a door lock capable of being readily installed in a door in such a manner that the combination can be easily changed when the door is open, but such that the combination cannot be changed when the door is closed.

A principal feature of my invention is a control circuit having a series of pushbutton switches arranged to present an actuating surface at the outside of the door, some of these pushbuttons being combination switches, and others comprising a reset switch and a lock switch; two other pushbutton switches, each arranged to present an actuating surface at the inside of the door, serve as lock and unlock switches; a series of code-setting switches; and a digital electronic network for deciphering the signals from the combination switches so as to actuate a latch bolt releasing mechanism if, and only if, the correct sequence is entered on the combination switches.

The entire circuit is packaged so as to fit into and become an integral part of a door, with attractive decorator panels on both the outside and inside of the door. The actuating surfaces of the pushbutton switches will then be the only parts of the control circuit presented at the outside surfaces of the door, and the code-setting switches will then be arranged in the perimeter of the door, accessible only when the door is open.

Additional objects and features of the invention will become apparent from the following detailed description and drawings, disclosing what is presently contemplated as being the best mode of the invention.

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The drawings FIG. 1 is a partially broken away perspective view, showing how the door lock of the invention is arranged to be mounted in a door;

FIG. 2, an end elevation view, also partially broken away for clarity;

FIG. 3, a view like FIG. 1, but exploded, with the circuit package shown removed from the door; and

FIG. 4, a schematic circuit diagram showing the circuitry of the door lock and the latching bolt.

Detailed description Referring now to the drawings:

In the illustrated preferred embodiment, the door lock of the invention is shown formed as an integral package, with ornamental plates 20 and 21 arranged to fit flush against the inside and outside faces of the door. These plates are larger than the interior body of the lock as shown in the drawings and effectively and attractively cover the opening in the door in which the package is inserted.

In mounting the lock, a section of the door 22 just as large as the interior body of the lock is cut out and the lock package will then be slipped into the cavity cut from the door with the ornamental plates 20 and 21 overlapping the opening cut into the door. Obviously, the distance between ornamental plates must be just slightly more than the thickness of the door, or must be made adjustable to fit assorted doors of various thicknesses.

The actuators of pushbutton switches PB-l thru PB-12 extend through, and their actuator surfaces are preferably fiush with, the surface of the outside ornamental plate 20, and the pushbutton switches PB-l3 and PB-14 extend through the inside ornamental plate 21 such that their actuator surfaces are flush with the surface of the inside ornamental plate.

Control knobs 24, of code-selector switches 8-1 through S-S, FIG. 4, protrude through an end plate 26, that is positioned between a latch bolt housing 27 and a member 28 both of which are affixed to the ornamental plates 20 and 21. The width of latch bolt housing 27 and member 28 define the interior body width of the lock and thickness of the door that the lock will fit.

A face plate 29 is adapted to be attached by bolts 30 to member 28 and to latch bolt housing 27 to thereby cover the control knobs and to reduce the possibility that they will be tampered with. Plate 29 also extends beyond member 28 and latch bolt housing 27 and screws 31, passed through the plate to secure the lock package to the frame of the door, as shown.

The circuit components, shown schematically in FIG. 4, are all mounted within the interior body of the lock. The end plate 29 can be readily removed and the settings of the code-switches S1 through S-S can be easily changed by turning knobs 24 when the door is open to allow access to its periphery.

The latching mechanism of the door lock comprises a latch bolt 36, FIG. 4, that is mounted to reciprocate in a bore 37, formed in housing 27. A spring 38, biases the bolt to its expelled position, and a solenoid 39, when energized, will act to retract the bolt into the housing. Bolt 36 has a recess 36a, formed in one side thereof, adapted to receive the end of a retaining pin 40. The retaining pin reciprocates in a bore 41, formed in housing 27 at right angles to bore 37. A spring 42, acting between the housing 27 and pin 40, biases the pin into the recess 36a of bolt 36. A locking solenoid 45, retracts pin 40 from recess 36a, thereby allowing bolt 36 to be expelled by spring 38. When solenoid is de-energized and bolt 36 is expelled, pin 40 rides against the bolt, and when the bolt is retracted, pin 40 is forced into recess 36a by action of the spring 42.

When bolt 36 is expelled it will fit into a conventional recess (not shown) in the door frame to securely lock the door.

The circuit of the door lock utilizes electronic components and is entirely silent in its selection operation so that it is impossible to detect whether or not the proper combination of pushbuttons is being actuated by sounds created, even with the use of a stethoscope or other sound magnification aid.

The circuit includes a combination switch section 46, including the pushbutton switches PB-l through PB-; a counter section 47, actuated in response to the pushing of any of the combination switches; a reset section 48, providing means for resetting the counter and logic network to the initial conditions necessary to operate the lock; and a logic network 49, for receiving signals from the counter and combination switches and for deciphering them to allow the latch bolt to be withdrawn if, and only if the signals are sequentially supplied in conformity to the setting of the code-selector switches S1 through 8-5. As shown, each pushbutton includes a bypass circuit including a resistor R and a capacitor 2, connecting the B voltage to a multivibrator F-l.

Counter section 47 is made up of three bi-stable multivibrators F1, F-2 and F-3 each including a diode D connected in series as a conventional binary counter. The purpose of the counter is to count the number of pushbuttons that have been actuated. Momentary closing of any pushbutton switch connects the multivibrator F-1 to ground to change its state. Each of the counter multivibrators is stable in one of two conditions. Looking at multivibrtaor F-l, for example: either a voltage of B is at K with zero voltage at A or a voltage of zero is at K and B voltage is at A. The state of the counter is designated by giving the three voltages that are B. Thus, the voltage combination outputs of the counter, corresponding to the number of counts resulting from pushbutton actuations are as follows:

The reset or zero condition is K 1 3 6;

one count is A F 6;

two counts is K B 6;

three counts is A B 6;

four counts is K fi C;

five counts is A fi C;

six counts is K B C;

seven counts is A B C; and

eight counts returns the counter to the reset condition Pushbutton switch PB-11 is the reset switch and will set the counter to the zero condition, K 3 6. The reset circuit also includes emitter follower 50. Whenever the reset condition, K F 6, is passed through leads containing diodes D present on the counter, a voltage will be produced out of emitter-follower 50 which will reset the logic multivibrators F-4 thru F-7. In this reset condition a voltage of zero is present on leads P1, P2, P3, and P4 of the multivibrators F-4 through F-7, respectively, and all of the logic multivibrators are thus reset through diodes D each time the counter reads K 6. Thus a person attempting to open the lock must provide the correct sequential combination in the first five combination buttons that are actuated after reset, or the process must be started over again.

The logic network, 49, includes four multivibrators, F-4 thru F-7 and the emitter-follower, EF-Sl. Each of the multivibrators and the emitter-follower has four inputs, three coming from the counter each containing a diode D and one coming from a code-selector switch. Only when all four of these input voltages are B will the multivibrators F-4 thru F-7 change states, thereby presenting a voltage of B at each of the leads P-l thru P-4,

respectively. It is noted that the three voltages coming from the counter to multivibrator F-4 correspond to one count, to multivibrator F5 to two counts, to multivibrator F-6 to three counts, to multivibrator F7 four counts and to emitter-follower 51 five counts. If the combination pushbutton that is activated first after reset and which changes the counter to state A 6 is the correct first number of the code, i.e. the number set on the codeselector switch S1, a voltage of B- is applied through code-selector switch Sl to the input of multivibrator F4. Since now all the inputs to multivibrator F4 are at B- its state will change and a voltage of B- will be presented at lead P1. If a pushbutton switch other than the correct one is activated first only three of the four inputs to F-4 will be at B and it will not change its state. The other multivibrators F5 through F-7 are similar to multivibrator F-4 and similarly will not change their states to have a voltage of B at their leads P2 through P4 unless the proper pushbutton has been actuated in the proper sequence.

If however, the first four numbers of the combination have been entered correctly, a voltage of B- is present at leads P1, P2, P3 and P4. It is necessary that all five inputs, each containing a diode D to an unlatching emitter-follower, 53, which serves as an AND gate and amplified, be at B, before a current will flow through the unlatching solenoid 39, which will be energized to retract the latching bolt, 36, in the manner previously described. Thus, if after the first four numbers have been entered correctly, the fifth number is also entered correctly, the four inputs to emitter-follower 51 will be at B and its output will also be B. All inputs to emitterfollower 53 will then be at B- and the lock will open.

The latching bolt 36 is retracted against the biasing effect of spring 38. When the bolt is completely withdrawn, retaining pin 40 will be biased into recess 36a by spring 42. Bolt 36 is thus held in its retracted position after the fifth pushbutton has been released, with a resultant deactivation of solenoid 39. The lock is thereby set in a passive open condition.

Pushbutton switch PB-12, which has an actuating surface exposed at the outside of the door 22, and pushbutton switch PB-13, which has an actuating surface exposed at the inside of the door, are the lock switches. The activation of either of these switches will energize solenoid 45 to retract the retaining pin 40. This will allow the latching bolt 36 to be expelled by spring 38 to its door locking condition.

To unlock a door equipped with the lock of the invention from outside the door, it is therefore necessary to first operate pushbutton PB-11 to be sure that the counter is set to zero condition. It is then necessary to operate five of the pushbutton switches P-1 through P-10, in proper sequence. If any but the proper five of the pushbuttons PB-l through PB-10 are operated, in the sequence determined by the setting of code-selector switches Sl through 8-5, the latch bolt will not be retracted.

As an example, if it is desired to use the combination 123-45, it must be set into the lock by positioning the movable contacts M of the code-selector switches as follows: 8-1 to position 1, 8-2 to 2, 5-3 to 3, S4 to 4, 8-5 to 5. Thus, contact M of code-selector switch 8-1 is then positioned to engage contact 1 to which a line, L-l, that is also connected to one terminal of pushbutton switch PB-l, is attached. The contacts M of code-selector switches S-2 through 8-5 are then positioned to respec' tively engage contacts 25 of the respective code-selector switch and lines L-2 through L-5 each respectively interconnect the contacts 2 through 5 and one of the terminals of the pushbutton switches PB-Z through PB-S. The contacts 110 of each of the code-selector switches are each respectively connected to a contact of each of the pushbutton switches via lines L1 through L-10.

The pushbutton switches PB-6 through PB10 have no function when the above described combination is used. However, if one of them is actuated the counter will step one count, but since there can be no simultaneous B voltage input from the combination switches to any of the logic elements, since PB-6 through PB10 are not connected through any of the code selector switches S-1 through S-S, multivibrators F4 through F-7 will not change states when pushbuttons PB-6 through PB-10 are actuated. If a mistake in the combination is made at any point, the reset switch PB-ll must be actuated and the combination started over again. An error will cause the counter to step one count but since one of the sequential voltage combinations from the counter has been generated without a simultaneous B- voltage application through a code selector switch, the logic element at which the error was made will not change state. The necessary voltage combination from the counter will not be available again until the counter has gone past the K D 6 condition which will automatically reset any of the logic elements set before the error was made.

In practice, with the combination described above set into the lock, it is first necessary to actuate pushbutton PB11 to insure that the counter is reset to its zero condition. Pushbutton PB-l is then actuated to change the counter to A F D and to simultaneously provide a voltage through S-l so that all inputs to multivibrator F-4 will be at a B voltage and it will change its state.

The sequential operation of the pushbuttons PB-2 through PB-4 will similarly sequentially establish the correct combination of voltages K B C, A B C and K F C from the counter and each of these, when simultaneously coupled with inputs from the respective pushbutton switches will make each of multivibrators F-S through F-7 change states. To complete the process, PB-S must be actuated. This will change the counter to A D C while simultaneously providing a B voltage through S-S. Thus all the inputs to emitter-follower 51 are a B voltage, and, therefore, its output is a B voltage. This, in turn, makes all the inputs to emitter-follower 53 a B- voltage, current will now fiow, energizing solenoid 39 and withdrawing the latch bolt so that the door can be pushed or pulledopen.

It should be obvious'that any of the pushbuttons PB-l through P B10 can be used in the combination, in any desired sequence.

If, for example, the pushbutton switch PB-IO was to be the first to be actuated in the combination, it would only be necessary to set the movable contact M of code-selector switch 8-1 to engage fixed contact 10 of the codeselector switch. The contact 10 is at all times connected to line L40 that is alsoconnected to one terminal of the pushbutton switch PB-10 and the positioning of movable contact M to engage it and closure of the switch would complete a circuit to supply an input voltage to the multivibrator F-4, through the pushbutton switch PB10.

Pushbutton switch PB-14, which has an actuating surface exposed at the inside of the door 22, is connected in Y a circuit that bypasses emitter-follower 53. When pushbutton switch PB-14 is energized the unlatching solenoid 39 is activated to retract the bolt. Retaining pin 40, which is riding against bolt 36 as it is retracted, is biased by spring 42 into recess 36a and the bolt is held open.

In a door lock, such as the one described herein, with S number of multivibrator and emitter follower units in the logic network and -P number of combination switches to choose from, the possible number of combinations is given by the formula N=P If, as in the above described lock, S is five and P is ten, there are one-hundred thousand possible combinations for the door lock. The number of possible combinations can be changed by increasing or decreasing either P or S.

-Multivibrators are completely silent as they change states. They may generate a small, transient electromagnetic pulse as they change states, but, this can be effectively shielded by a steel casing for the lock. Also, the counter multivibrators of the counter 47 change states with each pushbutton actuation, producing identical pulses that would tend to mask any produced in the logic network. Thus, the possibility of learning the combination from the outside by successive attempts is greatly reduced over mechanical type combination locks.

Although a preferred form of my invention has been herein disclosed, it is to be understood that the present disclosure is made by way of example and that variations are possible.

I claim:

1. A door lock comprising a plurality of combination switches arranged to have their actuator surfaces presented at the outside face of the door;

a reset switch arranged to have its actuator surface presented at the said outside face of the door;

a lock switch arranged to have its actuator surface presented at the said outside face of the door;

a plurality of rotary code-selector switches, each having as many contacts as there are combination switches;

a binary counter consisting of a plurality of bi-stable counter multivibrators connected in series, with the first one in said series being connected in parallel to each of the said combination switches, and each of the counter multivibrators connected to the reset switch;

means providing power through each of the combination switches to the first of the counter multivibrators;

a logic multivibrator corresponding to each codeselector switch, said logic multivibrators connected so as to have their states changed sequentially by the correct combinations of voltages from the counter and simultaneous voltage from the combination switches through the corresponding code-selector switches;

an automatic reset circuit that will reset all the logic and counter multivibrators to the initial reset conditions after a predetermined number of combination switches have been actuated;

an AND gate and amplifier for receiving voltages from the logic multivibrators and for producing a voltage to the unlatching mechanism if, and only if, all the logic multivibrators have had their states changed from their initial reset conditions; and

a solenoid controlled door latch, having its solenoid energized by the said voltage from the said AND gate and amplifier.

2. A door lock according to claim 1, wherein the door latch comprises a latching bolt;

a spring biasing said latching bolt to its door locking position; and

a latch-bolt solenoid energized by voltage from the AND gate and amplifier and retracting said bolt in opposition to said spring when energized.

3. A door lock according to claim 2, further including another circuit to the latch-bolt solenoid;

an unlocking switch in the said other circuit, having an actuator surface arranged to be presented at the inside of the door, whereby actuation of said unlocking switch will energize the latch bolt solenoid and move the latch bolt to its door unlocking position.

4. A door lock according to claim 1, wherein the code-selector switches are arranged to be mounted within the door with their adjusting knobs recessed into the perimeter of the door and accessible only when the door is open.

5. A door lock according to claim 1, wherein the latch mechanism also includes a solenoid controlled retaining pin that must be retracted prior to locking of the door latch;

an electric circuit to the solenoid of the retaining pin;

a locking switch in the said circuit having its actuator arranged to extend through the outside face of the door; and

another locking switch in the said circuit having its actuator arranged to extend through the inside face of the door, whereby actuation of either locking 8 switch will retract the locking pin to allow the door the code-selector switches are arranged to be mounted latch to move to its door locking position. within the door with their adjusting knobs recessed 6. A door lock according to claim 5, wherein the door into the perimeter of the door and accessible only latch comprises when the door is open.

a latching bolt; 5 a spring biasing said latching bolt to its door locking References Cited ii i i if d b h f th UNITED STATES PATENTS a ac 0 so enor energize l y vo age rom e I AND gate and amplifier and retracting said bolt in ggg gg Z 2 317-134 oppositionto said spring when energized. 10 19 7 W0 6 317 134 7. A door lock according to claim 6, further including another circuit to the latch-bolt solenoid; LEE Primary Exammer an unlocking switch in the said other circuit, having an A. D. PELLINEN, Assistant Examiner actuator surface arranged to be presented at the inside of the door, whereby actuation of said unlock- 15 'ing switch will energize the latch bolt solenoid and 278 move the latch bolt to its door unlocking position. 8. A door lock according to claim 7, wherein U.S. C1. X.R. 

